Tilting electric arc furnaces, for example as used in steel manufacture, are provided with a taphole through which an oxygen lance can be inserted and from which the molten metal passes when the furnace is tilted at the end of the melting process. Traditionally the molten metal is poured into a trough, or launder, accompanied by a quantity of slag which becomes unavoidably entrained in the metal stream. To overcome the problem of slag contamination, it has recently been proposed to provide the taphole with a hydraulically operated sliding gate valve mechanism which provides a positive shut-off for the metal stream at the end of the pouring step and effectively prevents the slag, which floats on the surface of the metal, from entering the ladle. Such a device is, for example, supplied by
Flogates Limited under the name FloCon Model 12800 Tap Hole Valve, and incorporates a collector nozzle.
The sliding gate taphole valve works well in practice, but, due to the extra length of taphole tube required to accommodate the valve mechanism and collector nozzle in certain types of furnaces, problems can arise due to turbulence in the metal stream, which adopts a jagged appearance and is difficult to pour accurately. Efforts to eliminate this problem have hitherto proved unsuccessful.